Field of the Invention
This invention relates to systems and methods for reducing I/O to redundant arrays of independent disks (RAIDs).
Background of the Invention
A RAID (i.e., a Redundant Array of Independent Disks) is a storage technology that provides increased storage functions and reliability through redundancy. A RAID is created by combining multiple storage drive components (disk drives and/or solid state drives) into a logical unit. Data is then distributed across the drives using various techniques, referred to as “RAID levels.” The standard RAID levels, which currently include RAID levels 1 through 6, are a basic set of RAID configurations that employ striping, mirroring, and/or parity to provide data redundancy. Each of the configurations provides a balance between two key goals: (1) increasing data reliability and (2) increasing I/O performance.
For short writes (writes less than a full stride), RAIDs may be subject to a phenomena known as “I/O amplification.” Specifically, when performing a short write to a RAID, old data may need to be read and compared (i.e., XORed) with the new data being written in order to calulate a parity delta. This parity delta may be used to update the parity value for the stride. Alternatively, data in the stride other than the new data may be read and used along with the new data to directly recalculate the parity value for the stride. In either case, a single short write may result in significantly more I/Os to backend storage devices making up the RAID, in effect “amplifying” the I/O to the RAID. These additional I/Os may slow down the RAID, increase traffic in the network, and increase wear and tear on backend storage drives.
In view of the foregoing, what are needed are systems and methods to more efficiently update parity information when making short writes to a RAID. Ideally, such systems and method will reduce the number of I/Os made to backend storage drives making up the RAID.